War on Weeds—weeds are everybody’s problem
Photo courtesy of Ohio State Weed Lab, The Ohio State University, Bugwood.org
THE ISSUE: Annual Bluegrass
Annual bluegrass (Poa annua) is a winter annual or short-lived perennial native to Europe. It can now be found around the world. It invades turfgrass, pastures, crop lands, and other moist areas. It can thrive in compacted soils, under heavy traffic, acidic soils, and in areas that are mowed short or overgrazed.
Annual bluegrass can grow up to a foot tall and has a bunch type growth habit. After germination it produces tillers that help it to expand its footprint. One of its most noticeable characteristics is its light green leaves, making annual bluegrass patches very noticeable when growing among darker green turfgrass species. Leaves are smooth on both sides and have a boat shaped tip. It is a prolific seed producer; a single plant can produce up to 360 seeds.
Integrated Pest Management (IPM) Options:
• Prevention— Learn to identify this plant. Never transport unknown plant material. Plant clean seed!
• Mechanical— Hand pulling seedlings prior to seed production can be effective on small infestations.
• Cultural— Plant competitive beneficial vegetation. Use management practices that will benefit desirable vegetation. Ensure that turfgrass is being irrigated, mowed, fertilized, and aerated properly to strengthen beneficial plants.
• Chemical— There are a few chemical control options. Unfortunately, we are limited by the fact that we are trying to control a grass that is growing alongside other desirable grasses. One option is to use a pre-emergent herbicide like Dithiopyr. Make the first application in early fall, apply a second application in early spring. Pre-emergent herbicides are used to control seeds as they germinate. This method may take several years to see success. Always read and follow herbicide label directions!
Justin Hatch, University of Idaho Extension Agriculture Educator in Caribou County. 208-547-3205
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